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Based on the analysis above, the helical cam will rotate 8 4 full circles to draw the bottom part, and then another 8 4 full rotations to draw the top part. In this process, we will need the paper cylinder to rotate 1 full circle for drawing the bottom part and another full circle for the top part. Therefore, we need to design a gear train with an overall gear ratio of 1:84, where the motor will direct drive the paper cylinder while the output shaft that spins the helical cam will rotate at 8 4 times the angular speed.
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